Advertise HTTP/2 protocol in Envoy via ALPN

[mariash]

Add the list of ALPN protocols that will be used by Envoy for
negotiation when connecting to applications.

#178805678

Co-authored-by: Merric de Launey [email protected]

What is this change about?

Executor now generates Envoy config with AlpnProtocols list as h2,http/1.1

What problem it is trying to solve?

It allows Gorouter to communicate with Envoy over HTTP2

What is the impact if the change is not made?

There would be no end to end HTTP2 support.

How should this change be described in diego-release release notes?

Update Envoy configuration to include http2 and http/1.1 ALPN Protocols

Please provide any contextual information.

Routing release issue - cloudfoundry/routing-release#200

Tag your pair, your PM, and/or team!

@weymanf

Thank you!

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[ameowlia]

• I noticed that you only added "h2" and "http/1.1" to the list of approved protocols in envoy.
• I know that Gorouter allows HTTP/1.0 traffic. See code here.
• However, I don't know if gorouter passes it through to the backend as HTTP/1.0 traffic.

❓ Have you tested to see if this breaks http/1.0 traffic?
❓ If not, can you?

[mariash]

@ameowlia there is a test in a gorouter. Even if you send HTTP/1.0 the backend will get HTTP/1.1. This is because golang http client Request will always send either HTTP/1.1 or HTTP/2. https://pkg.go.dev/net/http#Request

	// For client requests, these fields are ignored. The HTTP
	// client code always uses either HTTP/1.1 or HTTP/2.
	// See the docs on Transport for details.
	Proto      string // "HTTP/1.0"
	ProtoMajor int    // 1
	ProtoMinor int    // 0

Do we care about HTTP/1.0 if request comes not from the gorouter?